Jib cranes

ABSTRACT

A jib crane wherein the hook is mounted on the jib for movement along the length of the jib, power means being provided to effect said movement of the hook in response to the raising and lowering of the jib. The movement of the hook is controlled so that the distance between the hook and the pivot axis of the jib remains within predetermined limits as the jib is raised or lowered.

United States Patent [191 Quick Dec. 24, 1974 1 JIB CRANES [75] Inventor: Donald ,1. Quick, Queensland,

Australia [73] Assignee: International Harvester Company,

Chicago, Ill.

[22] Filed: Sept. 17, 1973 [21] Appl. No.: 398,917

[30] Foreign Application Priority Data Sept. 21, 1972 Australia 519/72 [52] US. 212/8 R, 214/130 R, 214/771 [51] Int. Cl. B66c 23/00 [58] Field of Search... 214/130 R, 130 A,130 B, 214/130 C, 762, 763, 771, 776, 777, 778, 141, 146.5; 212/9, 8 R, 8 A, 55, 58, 59, 35 HC [56] i References Cited UNITED STATES PATENTS 1,595,029 8/1926 Smith et a] 212/8 R 2,548,038 4/1951 Moliskey 212/8 R 3,352,441 11/1967 Alden 214/771 3,373,885 3/1968 Allison 212/8 R Primary Examiner-Robert J. Spar Assistant ExaminerLawrence J. Oresky Attorney, Agent, or FirmRaymond E. Parks; Floyd B. Harman [5 7] ABSTRACT A jib crane wherein the hook is mounted on the jib for movement along the length of the jib, power means being provided to effect said movement of the hook in response to the raising and lowering of the jib. The

movement of the hook is controlled so that the distance between the hook and the pivot axis of the jib remains within predetermined limits as the jib is raised or lowered.

2 Claims, 3 Drawing Figures JIB CRANES This invention relates to jib cranes and particularly to mobile jib cranes such as are commonly constructed upon a truck or tractor chassis.

It is common practice in the construction of cranes to provide on the jib several locations at which the hook may be attached, depending upon the load to be lifted. For stability and safety reasons, as the weight of the load to be lifted increases, the effective length of the jib (i.e. the distance from the point of attachment of the jib to the main frame to the line of lift of the hook) should be decreased. Thus, under normal operating conditions, it is frequently necessary to alter the position of the hook on'the jib, which in many cranes is not a simple operation, and results in an unnecessary wastage of time.

Another problem with the existing cranes incorporating a pivoted jib, is that as the jib is raised the effective distance between the line of lift of the hook and the pivotal axis of the jib decreases, thus moving the load closer to the-frame of the machine. This movement of the load during lifting frequently introduces difficulties, particularly with a bulky load which may foul a part of the machine.

It is, therefore, the object of the present invention to provide a jib crane wherein the position of the hook on the jib can be quickly and simply varied and once selected so that the distance of the hook from the machine remains substantially constant during raising and lowering of the jib.

In a crane having a jib mounted for pivotal movement about a horizontal axis to effect raising and lowering of a load, a hook mounted on the jib for movement to vary the position of the hook on the jib relative to the pivot axis of the jib, powered means to effect said movement of the hook, and control means arranged to actuate said powered means in response to the pivotal movement of the jib so as to increase said distance as the jib pivots in one direction and decrease said distance as the jib pivots in the oppositedirection.

Preferably, the control means are arranged so that the horizontal distance between the hook and the jib pivot axis remains within predetermined limits as the jib is raised or lowered.

Conveniently, the powered means is a double acting hydraulic cylinder and the control means includes a hydraulic valve controlling the supply of fluid to the cylinder. The valve is actuated through a linkage connected to the jib and the hook so that, when the jib is moved, the valve is actuated to energize the cylinder to effect a compensating movement to the hook and, when the required amount of movement of the hook is achieved, the valve is returned to a neutral position.

More specifically, there is provided a crane comprising a support structure, a jib mounted on said support structure for pivotal movement relative thereto about ment of the jib to effect movement 'of the hook carrier relative to the jib to increase the distance measured in the direction of the length of the jib between the hook and the jib pivot axis as the jib is raised and to decrease said distance as the jib is lowered.

In an alternative construction wherein the raising and lowering of the jib is effected by a hydraulic cylinder, a valve' may be arranged to meter fluid to jib lifting cylinder and the hook moving cylinder in accordance with the jib angle to effect a compensating movement of the hook as the jib is raised and lowered. Preferably, the control for the powered means which affects the movement of the hook can be operated manually independent of the automatic control means sothat the operator may initially position the hook inv the desired location on the jib having regard to the weight of the load to be lifted.

The hook may be mounted on a track or carriageway attached to the jib and extending in a general direction of the length of the jib, so that the hook may be moved along the carriageway by the powered means as required. Alternatively, the jib may be of a telescopic construction with one section pivoted to the main frame of the machine, and a hook carried by another section. In this construction, the position of the hook is varied by the powered means by extending or retracting the telescopic section. In yet another construction, the jib may comprise two articulated sections, the angular relations of which may be varied by the powered means, to achieve the required change in the position of the hook.

The invention will be more readily understood from the following description of one practical arrangement of a jib crane incorporating the variable position hook mechanism. This practical arrangement of the crane is illustrated in the accompanying drawings to which reference will now be made. 1

In the drawings:

FIG. 1 is a schematic representation of a mobile jib crane;

FIG. 2 is an enlarged view of portion of the jib and support frame, with a section of the jib broken away to a horizontal axis, means operably connected between the support structureand the jib to effect pivotal moveshow components 'of the mechanism disposed within the jib; and

FIG. 3 is a cross-sectional view takenalong line 3-3 in FIG. 2.

Referring now to FIG. 1, the crane comprises a vehicle 5 mounted on transport wheels 6 and carrying a jib 8 pivotally mounted at 9 to a support frame 10, mounted on the vehicle 5. The pair of hydraulic lift cylinders 13 are mounted between the support frame 10 so that the outer end of the jib may be raised or lowered by extending or retracting the hydraulic cylinder 13 to cause the jib to pivotabout the connection thereof to the support frame. The above described construction is typical of many well-known mobile jib cranes.

Suspended from the underside of the jib are a pair of parallel rails 15 attached to the jib by a plurality of longitudinally spaced bracket assemblies 16. The hook 18 is supported on a shaft 19 carrying apair of spaced rollers 20, which engage the respective rails 15. The length of the rails 15, and the disposition thereof on the jib is such that the hook may be moved along the track to any working position within the designed capacity of the crane, having regard to the load to be lifted at that particular position.

The double acting hydraulic cylinder 22 is mounted to the jib with the free end of the piston rod 23 of the cylinder connected to the shaft 19 from which the hook 18 is suspended. Actuation of the hydraulic cylinder 22 causes the rollers to move along the tracks 15 in order to vary the position of the hook 18 on the jib relative to the pivot axis of the jib. I

The telescopic control arm 25 is pivotally connected at the upper end to the bracket 26 secured to the jib, while the lower end of the control arm is pivotally connected to the lug 29 secured to the end of the piston rod 23 connected to the shaft 19. When the hook 18 is in its fully retracted position, that is, in its position closest to the pivot axis of the jib, the telescopic control arm 25 is in theposition shown in full outline in FIG. 2 and, as the hook is moved along the jib towards the fully extended position (shown in broken outline), the control arm 25 will pivot relative to the jib and retract andextend as necessary in accordance with the movement of the hook. The control arm 25 is connected via the rod 30 to one arm 31 of the bell crank 32, pivotally mounted on the bracket 34, attached to the jib. The other arm 36 of the bell crank is connected via the rod 38 to the spool 40 of the hydraulic control valve 41 mounted on the support frame 10. It will thus be seen that, as the jib pivots relative to the support frame and as the hook assembly moves along the jib, movement will be imparted to the spool 40 of the hydraulic valve The hydraulic valve 41 is connected via the line 45 to a source of pressurized hydraulic fluid, and via the line 46 to a hydraulic fluid storage tank. The respective ends of the double acting hydraulic cylinder 22 are each connected to ports of the valve so that fluid under pressure may be delivered to the respective ends of the double acting cylinder, depending upon the position of the spool of the valve, and fluid may be returned from either end of the cylinder to the storage tank.

'In operation, as the jib is raised and lowered by pivotal movement relative to the support frame 10, the bell crank 32 as a unit will pivot about the pivot axis of the jib, and thus effect movement of the spool of the valve. The direction in which the spool moves will be determined by'whether the jib is being raised or lowered, and the valve 41 is arranged to supply fluid to one or the other end of the hydraulic cylinder connected to the hook, depending on whether the jib is rising or falling. Thus, when the jib is being raised, the valve will supply fluid to the cylinder to move the hook outwardly from the pivot axis of the jib and vice versa.

The movement of the book along the jib by the hydraulic cylinder 22 will effect angular movement of the telescopic control arm and this will cause a pivotal movement of the bell crank 32 in the opposite direction to the movement induced by the pivoting of the jib. Thus, as the jib is initially moved, the cylinder 22 will be energised to move the hook 18 in a compensating direction and, as this movement is takingplace, the linkage will return the valve to its neutral position.

It can, therefore, be seen that movement of the jib will cause a compensating movement of the hook along the jib so that the hook will retain a substantially constant horizontal distance from the pivot axis of the jib, and also relative to the general frame of the machine.

In the embodiment illustrated, the hook is moved inwardly on the jib as the jibis lowered and vice versa, and thus, if the jib is lowered below the horizontal position, the hook will be moved closer to the machine frame as a result of the movement of the jib and this movement will be accumulative with the movement induced by the cylinder 22. The reverse action applies as the jib is moved upwardly to the horizontal position. The accumulating of the two hook movements in the below horizontal movement of the jib is of very minimal significance as the angle of movement of the jib is relatively small, and the combined movement has little effect on the stability of the crane when the jib is at a low angle. However, if required, the linkage mechanism may be suitablymodified to effect a change in the direction of hook movement as the jib moves through the horizontal position.

It will also be appreciated that a variety of mechanisms may be used to actuate the valve regulating the supply of fluid to the cylinder 22 which effects the movement of the hook, and that described above is merely one example.

I claim:

1. In a crane having a jib pivotally mounted on a frame for pivotal movement about a horizontal axis, a hook supported on the jib, means for moving the hook along the jib for positioning the hook at a preselected horizontal distance from the axis, means for pivoting the jib about the axis, and means for actuating the hook moving means, wherein the improvement comprises:

a first link having a plurality of substantially straight telescopic segments and being pivotally connected at the opposite ends thereof respectively to the jib and to the moving means;

a second link having a plurality of crank arms and being pivotally mounted between the arms on the jib adjacent the axis;

a third link having a substantially straight and rigid body and being pivotally connected at one end to one of the segments of the first link and pivotally connected at the opposite end to one of the crank arms of the second link; and

a fourth link having a substantially straight and rigid body and being pivotally connected at one end to another crank arm of the second link and pivotally connected at the opposite end to the actuating means for automatically operating the actuating means in response to pivotal movement of the jib for maintaining the hook at the preselected horizontal distance from the axis.

'2. The invention as claimed in claim 1, wherein the moving means include a pair of rails connected to the jib, carriage having rollers and riding on the rails, the hook being dependently mounted on the carriage, and a double acting hydraulic ram and cylinder unit having one end mounted to the jib and the other end mounted to the carriage; and, wherein the actuating means include a hydraulic valve mounted on the frame and having a flow control spool connected to the opposite end of the fourth link, and hydraulic pipe lines connecting the hydraulic ram and cylinder unit to the hydraulic valve and the hydraulic valve to a source of hydraulic fluid. 

1. In a crane having a jib pivotally mounted on a frame for pivotal movement about a horizontal axis, a hook supported on the jib, means for moving the hook along the jib for positioning the hook at a preselected horizontal distance from the axis, means for pivoting the jib about the axis, and means for actuating the hook moving means, wherein the improvement comprises: a first link having a plurality of substantially straight telescopic segments and being pivotally connected at the opposite ends thereof respectively to the jib and to the moving means; a second link having a plurality of crank arms and being pivotally mounted between the arms on the jib adjacent the axis; a third link having a substantially straight and rigid body and being pivotally connected at one end to one of the segments of the first link and pivotally connected at the opposite end to one of the crank arms of the second link; and a fourth link having a substantially straight and rigid body and being pivotally connected at one end to another crank arm of the second link and pivotally connected at the opposite end to the actuating means for automatically operating the actuating means in response to pivotal movement of the jib for maintaining the hook at the preselected horizontal distance from the axis.
 2. The invention as claimed in claim 1, wherein the moving means include a pair of rails connected to the jib, carriage having rollers and riding on the rails, the hook being dependently mounted on the carriage, and a double acting hydraulic ram and cylinder unit having one end mounted to the jib and the other end mounted to the carriage; and, wherein the actuating means include a hydraulic valve mounted on the frame and having a flow control spool connected to the opposite end of the fourth link, and hydraulic pipe lines connecting the hydraulic ram and cylinder unit to the hydraulic valve and the hydraulic valve to a source of hydraulic fluid. 